Field of the Invention
The present invention relates to a method of preparing an expression vector which permits simultaneous performance of the expression of retroviral genes and processing after translation, and the resultant plasmid and expression products available by such method of preparation. More particularly, the present invention relates to a method of preparing a plasmid, which causes expression of gag and pol genes of retrovirus by the application of recombinant DNA techniques, causes simultaneous processing of said expression product itself by a protease therein, and mass produces three kinds of core protein encoded by the gag gene, including p17, p24 and p15, and three kinds of enzymes encoded by pol gene, including protease, reverse transcriptase and integrase, individually and independently in the form of mature or active protein molecules, and the plasmid available by said method and expression products thereof. The present invention provides also a plasmid with a high expressing ability of nef gene and Nef protein molecule which is an expression product thereof.